This invention disclosure relates to electron emitters and more specifically to transmission mode negative electron affinity photocathodes and dynodes (secondary emissive devices). Photocathodes convert impinging radiation into a corresponding electron image whereas secondary emissive devices provide electron multiplication. Due primarily to the fragile nature of transmission mode negative electron affinity photocathodes and dynodes and the difficulty encountered in the fabrication thereof, commercial applicability and acceptability has been slow in materializing.
Electron emitting components, based on the negative electron affinity effect in cesium-oxygen treated single crystal semiconductor surfaces, have significantly better performance than conventional emitters in terms of sensitivity and resolution primarily due to their longer escape depths, higher escape probabilities, and narrower exit energy distributions. For a large number of pick-up tube applications (i.e., photomultipliers, television camera tubes, image intensifiers, etc.) transmission mode operation is required because this mode of operation greatly simplifies both the light and electron optics, thereby resulting in smaller and less expensive tubes.